This invention relates to a safety pressure release mechanism and a safety lock for pressure cookers.
The prior art discloses a variety of locking and pressure release mechanisms for pressure cookers. For example, Sebillotte U.S. Pat. No. 4,620,643 discloses a manually actuated safety device to prevent closure of a pressure valve if the handles of the cooker are not in the closed position and prevent opening of the lid when both the handles and the pressure valve are in a closed position. Chen U.S. Pat. No. 4,294,377 discloses a coupling steel ring and spring band on the cover of a pressure cooker that prevents the pressure in the cooker from exceeding a predetermined saturated pressure, thus keeping the pressure in the cooker constant. Brewer U.S. Pat. No. 4,840,287 discloses a pressure cooker locking mechanism having a camshaft assembly that prevents the cooker lid from being locked if the camshaft is not fully extended; a pressure responsive safety mechanism is also provided to prevent the opening of the locking mechanism when the cooker is under pressure.
Additional examples include Moucha U.S. Pat. No. 4,932,550, which discloses an interlock structure that prevents pressurization of the cooker if the lid is not securely attached to the cooker and prevents removal of the lid until the pressure in the cooker has dropped below a preset maximum. Seethaler U.S. Pat. No. 3,559,839 discloses a pressure cooker that is opened and closed by the rotation of upper and lower handles; the lower handle has a heat expandable element that urges a lock pin into a slot in the upper handle so that the cooker cannot be opened until the temperature has been lowered to a selected value and the lock pin has retracted from the slot.
Further, in Walker U.S. Pat. No. 4,103,801 the pressure cooker has a slidably mounted, manually operated lock member that must be unlocked in order to open the cover. Pressure in the cooker urges the stem of a sealing plug in the cover of the cooker upwardly and into engagement with the lock member when the handles are properly aligned and pressure builds in the cooker, thus preventing the cooker from being opened until the pressure decreases. A similar safety button is shown in the lid of Chen U.S. Pat. No. 6,257,124; when the cooker is under pressure, the safety button is positioned such that the lid cannot be manually opened. Zabel U.S. Pat. No. 4,257,394 discloses locking means connected with flanges in the lid and cooker body such that the lid will not rotate when the cooker is pressurized; a spring actuated relief valve is connected to a timer so that pressure is maintained in the cooker for a predetermined period of time after which the lid can be removed. In Demeyere U.S. Pat. No. 4,735,192 the cooker cannot be opened until the operator manipulates a knob, the movement of the stem of which allows a pin or peg to push a seal ring away from its seats, thus depressurizing the cooker and allowing the lid to be removed.
In Mendonca U.S. Pat. No. 6,105,808 a pop up valve prevents the lid from being turned to open the cooker when it is under pressure; the pop up valve also prevents pressure from building in the cooker if the lid is not properly installed on the cooker. Similarly, in Barrena U.S. Pat. No. 6,135,013 a valve remains in the up position when the cooker is pressurized and prevents a locking member from being released, and, in Elorza U.S. Pat. No. 6,067,896 a valve must drop in order to permit the lid to be opened. In Chameroy U.S. Pat. No. 5,370,259 the lid is sealed to the cooker via lock jaws; pressure developed during cooking is transmitted to internal faces of the lid, causing the lid and lock jaws to be forced together so that the lid cannot be removed until the internal pressure is reduced, and, in Chameroy U.S. Pat. No. 5,370,257, the cooker cannot be opened under pressure because a flow limiting valve, then in an up position, prevents the sliding of a latch or bolt that is necessary to open the cooker.
None of the prior art devices or patents, however, appear to provide: a simple guided means to reliably and safely install and lock the lid in sealing engagement on the cooker; simple, single-button means to relieve the pressure in the cooker, prevent the cooker from re-pressurizing, and unlock the lid of the cooker; means to automatically reset the various safety and convenience features of the cooker during the installation and removal of the lid of the cooker; positive latch means that allow an operator to perform other tasks while the cooker is depressurizing; means to automatically lock the lid on the cooker as it is being placed on the cooker; and means to make such a the cooker without the use of timers, pressure sensitive materials or parts, heat sensitive materials or parts, or moving parts that are preset to predetermined tolerances, pressure levels, heat levels, or weight levels so that they operate properly during pressurization and depressurization of the cooker.
The inventive cooker handle assembly contains an automatic pressure release system that allows the operator to press a button a first timexe2x80x94i.e., down to a first levelxe2x80x94in order to relieve the pressure in the cooker. Once the button is pressed down to the first level, a latch arrangement prevents the button from returning to its up position and, thus, prevents pressure from again building in the cooker. The latch arrangement must be reset in order to allow pressure to again build in the cooker, and, in order to reset the latch arrangement, the lid must be removed from, and then replaced on, the pot. Thus, the operator need not tend the cooker or continue to press the button in order to fully depressurize the cooker, but, may, instead perform other tasks while the pressure is being relieved.
Nevertheless, when the button is pressed to the first level, the lid is still locked on the pot and cannot be removed. In order to remove the lid from the pot, the same button must be pressed a second time, or downward to a second level, and held in the second position while the lid is removed. Premature removal of the lid from the pot is resisted by flanges on the lid and pot. The flanges are held tightly together when there is pressure in the cooker, which makes it difficult to rotate the lid off of the pot while the cooker is pressurized. The lid may be easily removed, however, when the cooker is depressurized, and the flanges are not as tightly held together.
The inventive handle assembly has upper and lower locking handles that are rotated into and out of alignment in order to, respectively lock and unlock the lid to the pot of the cooker. The upper handle is attached to the lid. The lower handle is attached to the pot. When the lid is rotated on the pot, a guide groove and spring-biased guide post in the handle assembly cooperate to guide the lid into a locked and sealed position on the pot and, simultaneously, set the latch arrangement so that pressure can build in the cooker. In addition, as the lid is being rotated on the pot, a spring-biased stopbar in the lower handle is pressed downward into a slot in the lower handle, allowing the upper handle and lid to rotate to the sealed position on the pot. However, when the lid reaches its sealed position, the spring-biased stopbar pops up into a slot in the upper handle and locks the lid on the pot.
The guidepost that guides the lid into a locked and sealed position is part of a lock guide that is housed and secured in an internal cavity in the upper handle of the cooker. The lock guide has an outward extending spring-biased spring post, an inward extending push post, and laterally extending latch dogs, as well as the downward extending guidepost. The downward extending guidepost extends down beyond the bottom of the upper handle and is aligned above and cooperates with the guide groove that is formed in the lower handle. The inward extending push post is aligned with a hole in the rim of the pot.
The upper handle also has an upper opening that receives and houses a button that is used to activate various features of the inventive handle. The button has, on its lower side, a downward extending, rounded tab that is aligned generally above a plunger or pin of a pressure relief valve that is installed in the lid. The button also has flexible, downward extending legs. The downward extending legs have latch arms that extend laterally from the sides of the legs. One of the downward extending legs of the button is longer than the other leg. The longer leg of the button is aligned immediately above the stopbar in the lower handle.
As the lid is rotated on the pot, the guidepost of the lock guide slides along a curved edge of the guide groove. As the guidepost slides along the curved edge of the guide groove, the lock guide in the upper handle is forced outward against the bias of the spring on the spring post of the lock guide. When the lid is fully rotated into its sealed position on the pot, the lock guide is positioned such that its laterally extending latch dogs are aligned below the laterally extending latch arms on the downward extending legs of the button.
When the button is pressed down the first time, or to its first level, the latch arms on the legs of the button are forced around and under the latch dogs of the latch guide and the downward extending, rounded tab of the button contacts and moves the pin or plunger of the safety relief valve, causing pressurized air and steam air to begin escaping from and depressurizing the cooker. In this position, the latch dogs of the latch guide are directly above the latch arms of the legs of the button and block the upward movement of the latch arms on the latch arms, thus preventing the button from returning to its up position and, in turn, preventing the rounded tab from moving out of contact with the pin or plunger of the safety relief valve. Accordingly, when the button is pressed once and is in its first position, the safety relief valve remains activated and does not permit pressure to be rebuilt in the cooker.
After the cooker is depressurized, the button is pressed down again, or to its second level. As the button is pressed down farther, the longer leg of the button comes into contact with the stopbar that is extended into the upper handle and pushes the stopbar down into its slot in the lower handle as long as the button is continuously pressed downward at the second level. When the stopbar is pressed down into its slot, the lid is unlocked and may be rotated back out of sealed engagement with the pot by rotating it in the opposite direction. As the lid is rotated in the opposite direction, the lower surface of the upper handle prevents the stopbar from moving upward, and the guidepost of the lock guide reverses it path along the curved edge of the guide groove of the lower handle. As the guidepost slides along the curved edge of the guide groove, the spring associated with the spring post of the lock guide biases and moves the lock guide inward. As the lock guide moves back inward, the latch dogs move out of alignment with the latch arms of the legs of the button and the button is permitted to move back to its up position. Thus, it is only when the lid is rotated off the pot that the latch arms of the legs of the button can be reset to a position above the latch dogs of the lock guide. When the lid is rotated sufficiently so that the lid and pot flanges are no longer one above the other, the lid may be removed from the pot.
In order to remove the lid from the cooker, the button must be pressed a second time. When the button is pressed a second time, the latch system permits a downward extending leg of the button mechanically depressing the stopbar into its housing slot to permit the lid to be rotated off of the cooker.